At the present day semi-finished products can be machined using various production technologies in a short period of time with very tight tolerances. The progress in the chip-forming and chip-less machining of workpieces can primarily be attributed to the rapid progress made in tool technology and machine tool technology. A machine tool is understood to be a machine that accommodates the tool and guides the latter relative to a workpiece. The tool is the component that is directly positioned against the workpiece that is being machined, in order to machine the latter. A multiplicity of different tools exist for various machine tools, for example, drill bits, milling cutters, grinding wheels, wires, chisels, thread cutters, etc.
The application of these tools ensues predominantly from their area of deployment. This will be illustrated with the aid of two simple examples.
Drill bits are, for example, tools that execute a rotational movement about their cylindrical axis (tool axis), while they are driven into the material with a feed rate parallel to the axis of rotation (feed direction). As the result of the combination of rotation and feed a tool-specific transport of material ensues. With their cutting edge spiral drill bits generate a chip that is transported by the spiral cutting edge to the surface. The feed movement thereby drives the drill bit ever deeper into the workpiece, while the cutting edge generates a chip in the drilled hole. Here the feed direction is identical with the tool axis.
Milling cutter tools are also rotating tools, usually operating at high frequency, for purposes of chip-forming machining. Depending upon the type of milling cutter, however, a workpiece can be machined by a milling cutter along more than one axis. In the same way as drill bits, milling cutters possess tool-specific parameters, the knowledge of which is indispensable for the rapid, efficient, cheap, and, above all, correct machining of a workpiece.
Grinding tools possess usually a plane surface, in particular, in the case of rotational movement, a circular surface. With the application of pressure they are moved onto the workpiece surface that is being machined, and remove the workpiece material correspondingly from the whole surface. Grinding pencils, in contrast, possess an abrasive sleeve surface, and thus have a curved tool surface.
In addition to the three types of tools that have been cited very many others also exist, all of which are manufactured for very particular machining conditions. Although the tools can be categorised with reference to their application, each type of tool in turn possesses various forms of embodiment. Thus, for example, roughing milling cutters exist for purposes of roughing out, that is to say, for the rough machining of workpieces, and finishing milling cutters exist for purposes of corresponding fine machining of the workpiece. Moreover, the same tools can be produced from different materials. It is obvious that workpieces of a particularly soft material should be machined with a tool that possesses a certain strength and hardness. In particular in the case of high-strength materials, such as carbide and nitride ceramics, it is ever more difficult to develop appropriate materials for the tools that are to be used for machining, since these must possess a very high hardness, strength and, above all, also toughness. The choice of the correct tool is therefore decisive for an efficient and correct machining of a workpiece.